The Cubs catcher had the biggest offensive game of his career on the day the team handed out 10,000 Contreras bobblehead dolls in an 11-2 rout against the tanking White Sox at Wrigley Field.

(Madeline Kenney/Sun-Times photo)

Manager Joe Maddon said it was only a matter of time until Contreras would break out. He has put in the work, and it has paid off as his swing has improved. He’s using more of a gap-to-gap approach now.

But none of those career-high 12 total bases or career-high seven RBI happened until the bobblehead arrived in the morning.

“You know what, more than anything, I just said, that’s absolutely correct,” Maddon said. “It had everything to do with the bobblehead.”

Contreras — who tripled twice and doubled in his previous game — opened with a grand slam to cap a five-run first, then added a bloop double to right in the fourth, a solo homer to left in the sixth and a two-run double to right in a four-run seventh.

“We all know what kind of hitter he is,” Kyle Schwarber said. “He’s an energetic player, and when he gets going, it brings a lot of energy to us. If he keeps this up, there’s going to be a lot of good things coming.”

Contreras, who had been the National League Player of the Week last August when he suffered a hamstring injury that cost him a month, is believed to be the first Cub with seven extra-base hits in a two-game span (records go back to 1913).

He also picked off Matt Davidson at second base for the first out of the third inning after starter Tyler Chatwood (3-3) walked the first two batters.

“It’s unbelievable,” said Chatwood. “I think we all knew it was coming. It was just a matter of time before he broke through.”

Contreras said it was just a “simple approach” that resulted in the big outburst. He saw a 37-point spike in his batting average and 127-point jump in slugging percentage.

“It’s just part of the game,” Contreras said. “Baseball is a game of ups and downs. It’s a matter of making adjustments.”

He became only the third catcher since the dead-ball era (pre-1920) with at least four extra-base hits and seven RBI in a game, according to ESPN Stats and Info, and the first since Mike Piazza in 1995. Cubs catcher George Mitterwald was the other, in 1974.

The Cubs picked up their fourth consecutive victory — three of them by blowout scores — during the seven-game homestand.

The Cubs’ sixth victory in their last seven games against the White Sox also included another torrid day at the plate for Kris Bryant, who hit his fifth home run in eight games on a day he reached base five out of six times.

Bryant has reached on a hit, walk or hit-by-pitch in nine of his last 11 plate appearances and 13 of 18 during the homestand (four games).

“When he’s on base, it sets it up for everybody else,” Maddon said of the No. 2 hitter in his lineup.

The Cubs’ 10 extra-base hits Wednesday and seven more Friday marked the first two games in which they’d hit that total since 2011.

Most of which started with Contreras — maybe even before the game began.

“I’m just really thankful to the team for giving me my bobblehead day,” he said.